The invention relates to a method for operating a cooling system of an internal combustion engine, and to a protection system in a cooling system.
The use of a controllable rotary slide valve with switched inlets permits considerably more flexible and faster regulation of the cooling system in relation to the use of conventional wax actuators.
It is sought, in a cooling system of an internal combustion engine, to realize the most dynamic possible control of the cooling system states, and in particular to be able to set the target temperature in the cooling system as accurately as possible, in order to reduce the emissions of the internal combustion engine. The potential that lies in the switching dynamics should in this case be fully exploited without reducing the functional reliability of the internal combustion engine.
It is an object of the invention to optimize the operation of a cooling system of an internal combustion engine.
This is achieved by way of a method for operating a cooling system of an internal combustion engine, in which a controllable rotary slide valve having at least one switched inlet or outlet is provided. The movement of the rotary slide valve into multiple switching positions which correspond to, in each case, one cooling system state is monitored. In a manner dependent on an improper functional state of the rotary slide valve and a present switching position of the rotary slide valve, an operating state of the internal combustion engine is changed to an emergency operation state.
Owing to the greater possible dynamics, the possibility of a prompt reaction in the event of faults during operation of the rotary slide valve is advantageous.
The monitoring of the rotary slide valve with regard to improper functional states permits a rapid and targeted change of the operating state of the internal combustion engine in order to protect the latter. Furthermore, such monitoring permits a differentiated reaction, such that the emergency operation state only has to be implemented in actually critical situations.
The emergency operation state permits only restricted functioning of the internal combustion engine, and includes for example a limitation of a rotational speed and/or a torque of the internal combustion engine to a predetermined maximum emergency operation value. The limitation of rotational speed and/or torque to the maximum emergency operation value may be performed entirely electronically.
Depending on the detected fault of the rotary slide valve and the present cooling system state, the emergency operation state may be implemented only temporarily or else may be implemented permanently until the fault is eliminated.
It is normally the case that various monitoring and control systems are provided in the vehicle, which are partially separate and partially integrated. For example, components such as the rotary slide valve are in each case connected to an actuation unit, which outputs control commands and which preferably controls the execution thereof. The activation unit diagnoses any faults of the respective component and communicates these to superordinate systems.
The superordinate systems include for example a thermal management system, the correspondingly programmed electronics of which define the cooling system states of the cooling system in accordance with the prevailing requirements by way of suitable specification of the position of the rotary slide valve. The thermal management system advantageously receives feedback regarding actual states of, for example, coolant temperature sensors in individual coolant branches, the present position of the rotary slide valve, and messages regarding any improper states of the rotary slide valve. The thermal management system advantageously has access to control electronics of the internal combustion engine in order to be able to in particular reversibly restrict the rotational speed and/or the torque.
Furthermore, a separate emergency operation management system is preferably provided, which is responsible for triggering a reduction of the torque and/or the rotational speed, as a protective function in certain situations, by accessing the control electronics of the internal combustion engine. The emergency operation management system preferably communicates with the thermal management system and at least with the actuation unit of the rotary slide valve. The emergency operation management system generally effects a permanent and restrictive limitation of the operation of the internal combustion engine in order to reliably prevent damage.
A further superordinate system is for example a general monitoring system of the vehicle which, inter alia, monitors temperature sensors in the cooling system with regard to an exceedance of a setpoint temperature. The general monitoring system preferably communicates with the thermal management system.
The handling of the entire process, from the detection of an improper functional state, via the recording of the fault in a fault memory, the signaling of the fault and the appropriate reaction, to a possible re-enablement of the operating states of the internal combustion engine, may be performed by the thermal management system itself.
In certain cases, it is however expedient to follow a more restrictive approach and to transfer the handling of the fault to the emergency operation management system, which for example keeps the operating state of the internal combustion engine permanently in the emergency operation state until the fault memory is restored in a workshop, and the rotary slide valve is repaired or exchanged.
It is possible, for example upon the next vehicle restart, to check whether the rotary slide valve is again functioning properly. If so, the emergency operation state can be ended again, both by way of the thermal management system and by way of the emergency operation management system.
Depending on the design of the rotary slide valve, it is possible for multiple subcircuits of the cooling system to be simultaneously entirely or partially opened or closed.
Here, it is advantageously the case that, in a proper functional state, the controllable rotary slide valve provides feedback regarding the present switching position, even with regard to partially opened or partially closed inlets or outlets. The respective cooling system state can be identified from the present switching position of the rotary slide valve.
The improper functional state of the rotary slide valve may be defined for example by a movement stiffness of the rotary slide valve, a jamming of the rotary slide valve, a failure of an actuation unit of the rotary slide valve, or a failure of a position detector of the rotary slide valve.
The type of improper functional state, and the cooling system state defined by the present switching position of the rotary slide valve, are crucial for the reaction that is implemented.
One possible critical present switching position of the rotary slide valve corresponds, for example, to a state of the cooling system in which the vehicle cooler (radiator) is at least substantially not traversed by flow. In this case, at most a part of the maximum cooling power is available, and in the case of a high-power demand, that is to say in the case of high-torque and/or high rotational speed of the internal combustion engine, it would be possible for the coolant temperature in the internal combustion engine to rise to an excessively high value. In this case, the internal combustion engine is advantageously placed into the emergency operation state in order to prevent an excessive temperature increase. The initiation of the emergency operation state may possibly be made dependent on further parameters.
A present switching position of the rotary slide valve which corresponds to a state of the cooling system in which a flow through coolant lines in the internal combustion engine is at least partially throttled is to be regarded as being particularly critical. In this switching state, it is normally also the case that the vehicle cooler is not traversed by flow, such that the cooling power of the internal combustion engine is restricted almost or entirely to the minimum cooling power. Intense increases and power of the internal combustion engine could, in this state, lead to overheating. In this case, a rapid and highly restrictive switch to the emergency operation state is recommended.
It is preferably the case that a coolant temperature is detected, and that the operating state of the internal combustion engine is changed to the emergency operation state only above a threshold value temperature.
It is expedient for the coolant temperature to be detected in the region of a cylinder head of the internal combustion engine and/or for a coolant temperature in a coolant line immediately downstream of the internal combustion engine to be detected, that is to say at locations at which the maximum coolant temperature prevails.
If the coolant temperature still lies below the threshold value temperature, the thermal management system may decide that a restriction of the operating state of the internal combustion engine will not yet be performed.
In the above-described particularly critical cooling system states in which the cooler and possibly also the internal combustion engine are not traversed, or are only partially traversed, by a flow of coolant, it is however preferable for the emergency operation state to be immediately initiated regardless of the coolant temperature. This may also arise in the case of improper functional states, that is to say faults of the rotary slide valve which are highly probably permanent and which cannot be eliminated during ongoing driving operation or by way of a restart of the vehicle, for example in the event of the failure of a position detector or of control electronics. The initiation of the emergency operation state may, in such situations, be realized directly by way of the emergency operation manager which receives the respective fault message from the actuation unit of the rotary slide valve, in order to realize the most prompt possible reduction of the heat generation by the internal combustion engine.
In the case of an unthrottled or only partially throttled coolant flow through the vehicle cooler, the emergency operation state can be withdrawn again if the temperature falls below the threshold value temperature. In this case, it is in principle the case that adequate cooling power is available even for relatively high engine speeds and torques of the internal combustion engine. In this case, it may suffice for the coolant temperature to be monitored and for the operation of the internal combustion engine to be restricted only if the coolant temperature exceeds the predefined threshold value. This may be the case for example in the event of brief instances of demand for high power.
An initiation of the emergency operation state may be at least initially permitted if, in the present cooling system state, at least a minimum flow through the vehicle cooler is realized, even if the rotary slide valve is in an improper state, as long as the coolant temperature lies below the threshold value temperature. In the case of the vehicle cooler being partially or fully open, the cooling action is normally adequate for all operating states of the internal combustion engine, that is to say all rotational speed ranges, such that an intervention is necessary only if the coolant temperature rises to too great an extent.
In the case of the vehicle cooler being fully open, and thus in the case of a maximum coolant throughflow, it is possible here to wait for a possible fault message from the general monitoring system of the vehicle, and to implement the emergency operation state only when the general monitoring system responds.
In the case of a partial flow through the vehicle cooler, that is to say in cooling system states with a throttled coolant flow, however, the temperature monitoring is preferably performed by the thermal management system in order to shorten the reaction time before the start of the emergency operation state.
In the case of an improper functional state of the rotary slide valve which is defined by a failure of the position detector of the rotary slide valve, the rotary slide valve may be moved into a predetermined switching position in which the coolant lines in the internal combustion engine are traversed by a flow of coolant. Even if it is no longer possible to obtain reliable feedback regarding the present position of the rotary slide valve, it is possible in many cases for the rotary slide valve to be moved further into a known switching position in which, advantageously, an at least partial flow through the vehicle cooler and/or through the internal combustion engine is realized.
This may be realized for example by way of a movement of the rotary slide valve as far as an end stop. The arrival at the stop may be identified by way of an increased power consumption of the control motor that moves the rotary slide valve.
It is also possible for the rotary slide valve to be moved for a certain time period based on the assumption of the last known switching position, and then, if necessary, for the switching to be at least approximately determined through monitoring of the present coolant temperature.
Alternatively, the last known switching position may be assumed as a present switching position, and the rotary slide valve may be completely deactivated, that is to say locked. The setting of the operating state of the internal combustion engine is in this case performed in accordance with the last known switching position, and possibly the presently measured coolant temperatures. In this case, the emergency operation state is preferably initiated.
The improper functional state of the rotary slide valve referred to as “movement stiffness” is detected if the movement to a second predetermined position from a first predetermined switching position exceeds a setpoint time. As a reaction, a shaking-free step is preferably performed, in which the rotary slide valve is moved quickly between different switching positions multiple times in order to overcome the blockage. The shaking-free step may basically always be performed. Since it however takes a relatively long time, for example up to 20 seconds, it is preferable, in the presence of cooling system states with a throttled coolant flow through the internal combustion engine and possibly through the vehicle cooler and/or with an excessively high coolant temperature, for the emergency operation state to be initiated, that is to say for the rotational speed and/or torque of the internal combustion engine to be reduced, in order to be able to ensure adequate cooling power.
If the shaking-free step is successful, the operating state of the internal combustion engine can be re-enabled by the thermal management system. However, if the shaking-free step is not successful, the thermal management system preferably registers the fault state “jamming”, and makes a decision regarding an enablement of the operating state or an initiation of the emergency operation state on the basis of the present switching position of the rotary slide valve and possibly the present coolant temperature.
In the improper functional states of the rotary slide valve and in the case of the emergency operation state of the internal combustion engine being implemented, a fault message is advantageously stored in a fault memory, and/or a fault display is triggered. The storage may be performed in a fault memory of the thermal management system, of the emergency operation management system and/or of the general monitoring system, where it can be read out by technical personnel during a workshop visit. Furthermore, it is possible for warning lamps and/or warning indicators on the dashboard to be activated in order to inform the driver. It is possible for different warning lamps and/or warning indicators to be provided for the emergency operation management system and for the thermal management system.
The method just described may be carried out for example by way of a protection system in a cooling system of an internal combustion engine, wherein the protection system includes a thermal management system, which receives and processes coolant temperatures, and an actuation unit of a switchable rotary slide valve with a position detector which can detect a present switching position of the switchable rotary slide valve, wherein the thermal management system is connected to the actuation unit of the rotary slide valve.
It is preferably the case that, in addition to the thermal management system, an emergency operation management system separate therefrom is provided, which communicates with the thermal management system. The emergency operation management system is preferably connected directly to the actuation unit of the rotary slide valve, and designed such that it can of its own accord, and independently of the thermal management system, trigger an initiation of the emergency operation state.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.